Lawn aeration: why, how and when to do it

The biggest focal point of a garden is probably the lawn: we all want ours to be luxuriant, level and lusciously green. On the contrary, stunted, sparse or yellowed grass is a clear indication of poor lawn health, in addition to being unsightly.

A lawn can suffer from poor maintenance, as well as from choosing the wrong type of grass seed. One often neglected activity is lawn aeration (or airing). In today’s article we explain what it is, why it’s important and how to do it, before sharing some tips on keeping your lawn beautiful and healthy between one airing and the next.

What is the purpose of lawn aeration?

Lawn aeration serves primarily to break up and remove thatch. Thatch is the blanket of organic material (leaves, clippings, root fragments and various plant debris) that settles on grass over time, where it continues to accumulate when the soil is no longer able to decompose it.

When it is up to 3-4 mm thick, thatch works like mulch, which reduces the evaporation of moisture from the ground: this is good for your lawn, especially in summer. Beyond that thickness, it becomes an insidious barrier to the health and beauty of the grass, by:

• preventing penetration of light, oxygen and water (which therefore becomes stagnant)

• forcing grass to grow taller in search of light

• making irrigation, fertilisation and reseeding less efficient.

In practice, with less light, water and nutrients available, lawns become more vulnerable to disease and less resistant to summer drought and the rigours of winter.

So what does aerating the garden involve? Lawn aeration eliminates thatch (also known was “dethatching”), thereby restoring oxygen to the grass roots, allowing the soil to absorb water and nutrients and enabling grass seedlings to effectively photosynthesise. More vigorous aeration—verticutting and soil scarification—involves using a special bladed machine to make slits several millimetres or centimetres deep into the soil. This thins out the grass, facilitating the circulation of oxygen, water and nutrients.

Aerating your lawn doesn’t just remove thatch. It also eliminates moss, which suffocates grass, especially in shaded areas, wherever there is stagnant moisture and free space.

Thatch and moss are not the lawn’s only enemies: weeds are an equally constant menace. Here you will find an overview of the various ways to get rid of weeds.

How and when to aerate or scarify the lawn

So, how and when should you aerate or scarify the lawn? From the second/third year of a turf’s life cycle. The best times of year to aerate are the beginning of spring (February-March) for warm-season grasses, which thrive in warmer climates, and late summer/early autumn (September-October) for cool-season grasses, which are more compatible with cold/humid climates. The temperature shouldn’t be too hot or too cold, because the grass needs the right conditions to recover quickly.

How often should you aerate the lawn? It depends on the type of grass, the soil characteristics and the lawn’s intended use. If the soil is clayey and therefore has a tendency to compact, it should be aerated at least once a year; whereas, if it is sandy you can air it every other year. Whatever type of soil you have in your garden, consider how much it is affected by other possible causes of compaction, such as frequent trampling and passing cars.

So, how should you aerate the lawn? Here are the steps you should follow for perfect aeration:

• Cut the grass very short (around 3 cm) and collect the clippings.

• If there is moss, spread an iron-based moss control product and, before aerating the garden, wait for it to dry.

• If necessary, wet the lawn: the scarifier blades work more easily when the soil is damp (but not soaked).

• Proceed with aeration: if the soil is clayey or hasn’t been aerated for some time (at least a year), we advise making a second pass perpendicular to the first.

• If your lawn aerator lacks an integrated collection system, collect the thatch with a rake: you can then use it to make compost.

• Feed the grass by spreading lawn fertiliser containing nitrogen (this is the most important ingredient), potassium and phosphorus: the grass needs to recover quickly from the stress of low cutting and aeration in order to continue growing and cover the holes made in the lawn, as well as any gaps left by the removed moss.

• Re-seed (or overseed) if the lawn is very thin or the removed moss has left behind large patches of bare ground.

What tools should be used to aerate the garden? If the lawn is small, you could make do with a manual lawn scarifier (or aerator), which is a kind of rake equipped with blades that is rather challenging to use.

Alternatively, especially if you have a large garden you can opt for a motorised scarifier, with any of the following features:

• Spring tines that dethatch the lawn by combing it, breaking up and lifting thatch and any moss encountered

• Fixed blades: not only dethatch but also scarify or “verticut” the ground, by cutting slits to an adjustable depth

• Towed: the Oleo-Mac spring-tine scarifier can be hooked to the MH 155 K compact rotary tiller, converting it into a practical lawn aerator.

How to prevent thatch

Now you know how to aerate your garden, but can you prevent or reduce the formation of thatch? Yes, by following these tips:

• Keep your lawn clean by raking it regularly from spring onwards.

• When pruning trees or thinning out hedges, remove even the smallest clippings from the grass, ideally using a blower, which in autumn is also invaluable for eliminating dead leaves.

• When mowing the lawn, collect the clippings with the grass catcher on your lawnmower or garden tractor or, failing that, with a rake.

• Leave the clippings where they are only if they have been mulched (by a lawnmower/garden tractor with this function): make sure that the mulch is evenly distributed, without forming piles.

• Use mulching only as long as the season permits: after summer it is preferable to collect the cut grass, because temperatures are generally too low for it to decompose fully, and it is more likely to rot in autumn when the climate is typically damp.

Speaking of summer, this is a delicate time for lawns. Drought and heat make it difficult for grass to survive, but proper mowing helps to keep it healthy. Check out our tips on how to mow the lawn in summer.